The research is also published online by the New England Journal of Medicine, alongside a recommendation from the team that preimplantation should no longer be performed routinely in older women undergoing IVF.

People aiming for a test-tube baby can pay thousands of dollars for a preimplantation genetic screening test.

The idea is to study the genetic make-up of embryos before transfer to the womb to make sure they are healthy and likely to survive.

But Dutch researchers found screening in women aged 35-41 years makes matters worse.

After 12 weeks, only 25% of women undergoing IVF whose embryos had been screened were pregnant, against 37% in the control group. Eventual live birth rates were also lower, at 24% versus 35%.

Just why screening cuts the chance of a viable pregnancy is unclear but Mastenbroek says the test itself might be to blame.

"It is possible that the biopsy of a cell from an early embryo on day three after conception hampers the potential of an embryo to successfully implant, though the effect of biopsy alone on pregnancy rates has not been studied," he says.

Usually, embryos will have reached the eight-cell stage of development by day three but sometimes there may be as few as four cells, which could in theory make the procedure riskier.

Other factors may be the limited number of chromosomes that can be analysed, which may lead to the transfer of embryos that appear normal but in fact contain faults.

Also many embryos are 'mosaic', where a single cell does not properly reflect the genetic make-up of the whole.

Fertility experts say the findings are a wake-up call for clinicians and show the need for more research into the benefits, if any, of preimplantation genetic diagnosis.

Peter Braude, professor of obstetrics and gynaecology at Kings College London, says the work shows screening does not work in older mothers-to-be and similar studies are needed on whether it helps younger women with repeated IVF failure.

"Vulnerable patients should no longer be exploited financially under the impression that it works," he says.

Professor Joep Geraedts, the ESHRE's next chairperson, says the new study will come as a shock, particularly in the US, where preimplantation genetic diagnosis is widely used.